1. Field of the Invention
This invention relates to vinyl caprolactam monomer (V-Cap), and, more particularly to free-flowing flakes of such monomer which is usable below its melting point of 34xc2x0 C. without developing coloration, to coating and adhesive formulations thereof, and to cured, optically clear coatings thereof.
2. Description of the Prior Art
Vinyl caprolactam monomer presents a challenge in terms of handling and formulation because it is a crystalline solid at room temperature (m.p. 34xc2x0 C.). The monomer is usually stabilized by an amine that prevents homopolymerization during storage. However, the amine stabilizer imparts color when the monomer is stored for an extended period of time at room temperature or for a short period at an elevated temperature. The color of the monomer also increases dramatically when stored above its melting point.
Vinyl caprolactam also exhibits an interesting phenomenon known as xe2x80x9csuper-coolingxe2x80x9d, which allows it to exist as a liquid below its melting point under certain conditions. Two factors that contribute to super-cooling are the lack of crystallization sites or xe2x80x9cseedsxe2x80x9d and an infinitesimally slow cooling rate. These conditions, however, are almost impossible to achieve in an industrial environment in the containers used for drumming. Hence, vinyl caprolactam users are forced to melt the monomer before subsequent handling. This melting step also increases the color of the material due to chemical reactions attributed to the amine stabilizer and trace impurities in the monomer.
Accordingly, it is desired to provide vinyl caprolactam in a form that is easy to handle, does not require energy-intensive melting before use, and that does not acquire a colorant during handling or storage.